(any Flatpak user would’ve at some point run into annoying sandboxing limitations - such as password manager and browser integration, or themeing woes)

While I overall do prefer Flatpak over AppImage these days, the sandboxing has indeed been giving me more trouble than I think it is worth so far.

I’m not aware of any distro that automatically clears a user’s .cache in their home directories. Maybe you’re thinking of /var/cache?

Personally I’ve been happy with the Nokia branded phones (manufactured by HMD Global).